This is a good video that can help explaining why transition from sim trading to trading with real money takes some planning and efforts to smooth out the process. My advice – treat sim trading as seriously as you can similar to what pilots do while in training with their flight simulators. This will make sim trading working to your advantage instead of implanting bad trading habits.
Jonathan Bricker is a researcher on behavioural change. His work shows that discipline alone is not enough to induce changes on negative behaviours or habits. Instead, having a strategy based on acceptance and commitment allows for much better chance of success in permanent behavioural changes.
For traders who have impulsive behaviour like over trading and deviation from their trading plan during trading, it is a good introduction on what is necessary to correct the behaviour.